The term annunciator panel most commonly refers to a group or array of warning or advisory indicators in an aircraft cockpit. These indicators “announce” to the pilots any of a number of issues of importance regarding the aircraft's systems or flight progress. Most annunciator panel layouts group warning indicators according to the systems they serve or, in the case of newer aircraft, in color coded ranks of urgency. Some annunciator indicators require a reset when they activate; others simply illuminate for a short period and some require a specific action to be carried out before they reset automatically. Traditional incandescent lamp annunciator panels are being replaced by digital indicators on in-panel displays on newer, glass-cockpit equipped aircraft.
The annunciator panel is often also referred to, rather unflatteringly, as an idiot light panel and serves to bring a variety of flight and aircraft system issues to the attention of the pilot. These issues will generally be grouped into advisory, caution, and warning categories and each with its own required course of action. Many aircraft types feature annunciator panels with most of these indicators grouped together, although others may have several groups arranged around the instrument panel. In general though, the annunciator panel is typically located centrally in the cockpit and often features audible warnings to accompany the visual indicators.
Typical annunciator panel advisories include system status indicators such as anti-icing, auxiliary power unit (APU) status, pitot, and fuel heating systems. These annunciator lights simply give an instant, visual indication of whether the relevant systems are active or not and generally require no specific action be taken. Cautionary annunciator indications typically include fuel, cabin pressurization, target altitude, engine, electrical, and hydraulic system alerts which give pilots early warning of potentially hazardous system developments which require intervention on their part. Annunciator panel warnings are the most serious of all indicators and include fire and system failure warnings which call for immediate action.
These groups of annunciator panel lights will typically be color coded according to their advisory, caution, and warning status. Advisories are white, blue or green, cautions are yellow or amber, and warnings are red. Most cautions and all warnings will also be accompanied by an audible tone. These groupings and their associated color codings have been maintained in most modern engine indication and crew alert system (EICAS) equipped aircraft. On new systems, many of the traditional annunciator panel lights are being replaced with digital readouts on one or more multifunction display units (DUs).